Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009aas...21349122m&link_type=abstract
American Astronomical Society, AAS Meeting #213, #491.22; Bulletin of the American Astronomical Society, Vol. 41, p.470
Astronomy and Astrophysics
Astronomy
Scientific paper
We are analyzing the pumping mechanism that may be responsible for the production of two bright UV lines of Fe II at λ=250.75nm and λ=250.91nm in the B and D Weigelt blobs of Eta Carinae, as well as for the production of two bright 1.7 μm lines (whose localization in the expanding envelope of the star is not certain). The current explanation [e.g. Johansson & Letokhov, 2007] is based on the hypothesis that the Ly-α photons produced by ionization and cascade recombination of hydrogen and trapped in the blobs drive the pumping cycles due to the "accidental resonance” of these photons with the UV transitions of Fe II that start the cycles. A strong broadening of the Ly-α line due to the multiple scatterings of the photons is crucial to this model because the "resonance” is not precise. Here, we consider an alternative model based on direct pumping by the diluted continuum of the star. We show that the number of the UV photons from the star driving the fluorescence cycles directly is sufficient for providing the observed intensities of the two bright UV lines. We also demonstrate that the diluted black body continuum of the star can create an inversion of populations in the 1.7 μm transitions for the observed projected distances of the blobs from the star. However, possible laser amplification is strongly limited by the insufficient optical depth and/or by saturation. Observations of the two IR lines with higher spatial resolution are needed to discriminate between the possible lasing and the thermal or fluorescent radiation. This project was supported by the NSF/REU grant AST-0354056 and the Nantucket Maria Mitchell Association.
Messenger Stephen J.
Strelnitski Vladimir
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